Sounds like you just didn't quite get your metal hot enough. It also
sounds like it was just hot enough to get your job done. Nickel
alloyed white golds are somewhat temperamental. A few impurities,
overheating .. soon there is an uynworkable lump that cracks in the
early stages. I like to pour ingots. They provide a more uniform
roll which is especially important when first rolling out metal.